Making an impact

18 October 2023

If you spend most of your time on a construction site, you’ll know that hitting your head can be part of the job. Most of the time, it’s minor bumps, but sometimes it can be harder hits. Common accidents can be knocks to the side of the head, falling objects, slips, trips or falls. These can be angled impacts, and angled impacts can create a rotational motion, explains Chris Tidy.

WE’VE ALL seen the headlines about head injuries in sports: In elite rugby, football, NFL and boxing, leading to potentially severe cases, long-term issues and degenerative brain conditions caused by multiple head impacts, known as sub-concussions. Most of us risk head injury at work and in play. Some face this risk more than others, like those who work within the construction, industrial and utility sectors.

Helmets have been used to protect people in one form or another for thousands of years. From their humble beginnings as battle armour in 2,500 BC to today, where their use is much more widespread, they have stood the test of time. Despite having one of the highest wearer compliance rates of all PPE products and the widespread and mostly mandatory use of hard hats, construction and industrial workers are still at risk for severe head injuries, including concussions. Our most valuable asset is our head because that is the bit that works everything else. If something happens to our head, there may be serious implications, including anything from brain injury to death.

Traditional safety helmets are developed and tested for straight impacts, but studies have shown that the brain is more sensitive to rotational motion (angled impacts) than linear motion (straight impacts). Rotational motion can be dangerous and result in traumatic brain injuries (TBIs). When rotational motion is involved, even impacts that might be considered light can cause concussions due to the brain’s sensitivity.

The most common type of TBI is a concussion, which accounts for up to 75% of all TBI cases. These injuries are far more common than you think; 50% of TBIs go undiagnosed or detected, while 90% of diagnosed TBIs do not involve a loss of consciousness.

Whether the head impacts the ground after a slip, trip or fall, or if a falling object hits the head, it is likely to be an angled impact, which could introduce a rotational motion to the head. Conventional hard hats are designed to protect against injuries such as skull fractures but are often not designed to address rotational motion.

Injury statistics show that it is most common to fall at an angle when you fall and hit your head, compared to a linear fall. Falling at an angle creates rotational motion, and science has shown that our brains are particularly susceptible to rotational motion. In an angled impact, these motions may transfer to your head.

The human brain is amazing – but sensitive, especially to rotational motion. Almost all head impacts generate rotational motion, which can cause strain on the brain tissue, which may lead to minor or severe brain injuries. Concussions or even more serious brain injuries are commonly caused by rotational motion transferred to the brain. The moment your head is hit by an object or hits the ground at an angle, it can be forced to start rotating more or less, depending on the impacting object or surface. If the rotational motion generated is transferred to the brain, it can cause injury to the brain tissue or the blood vessels connected to the brain. 

The brain is more sensitive to rotational motion than linear motion because it has shear properties similar to water or gel. When different parts of the brain move relative to each other due to rotational motion, the tissues can stretch, which can cause concussions or other brain injuries. Our brains consist mostly of water. The brain and the cerebrospinal fluid fill up most of the skull. Water is incompressible, so the brain will not move much from a straight impact. However, most angled impacts introduce a rotational motion to the head. Rotational motion to the head causes the brain to rotate inside the skull. This causes a relative movement between the skull and the brain, which can cause tear of blood vessels as well as strain in the brain and can cause a TBI.

Many of us have seen EN397 safety helmet shock tests where a linear force is directed onto a safety helmet from height, and in most cases, the hard hat remains intact. This test is a sobering reminder of the importance of wearing head protection and demonstrates that these safety helmets are relatively good at absorbing linear impacts. The problem is that most traumatic head injuries are not caused by a linear impact on the crown of the safety helmet. When falling objects cause injuries, they rarely fall straight down and cause a linear impact.

Helmet technology company Mips is already well known in sports and motorcycle helmets and is popular among skiers and cyclists. It has partnered with leading PPE manufacturers globally to incorporate a patented low-friction layer into their safety helmets. The low-friction layer is designed to allow the head to move inside the helmet (10–15 millimetres relative motion in all directions), intended to help redirect harmful rotational motion of certain impacts that would otherwise be transferred to the head. The intention is to help reduce the risk of brain injury. 

How the Mips safety system works 

Everything revolves around the low-friction layer. It mimics the brain’s own safety system, which allows the brain to move slightly inside the head. The system is designed to work on the same principle. The low-friction layer is built into the helmet, making the outer parts of the helmet, the shell and the energy-absorbing layers (the “padding”) mobile so that the head can move 10–15 mm inside the helmet on impact.

We need to understand more about the different levels of safety that hard hats provide. Although we see high compliance and usage, employers and end-users often default to the lowest-cost solution when procuring safety helmets, as long as they meet the standard. The standard is only the minimum level required. To prevent head injuries onsite, we must first understand the risk. This involves educating the supply chain and changing the whole industry perspective. There are a lot of accident records and statistics available online; however, interpreting these is key to understanding and evaluating the risk.

We must continue pushing for better, more detailed accident reporting and statistics to take steps to help people stay safe and ensure we focus on the areas that can have the most significant impact on wearer safety, such as traumatic brain injury (TBI) and rotational injury.

Mips works closely with helmet manufacturers, distributors, safety professionals and industry institutions to encourage best practices around PPE and awareness of head injuries and educate on real-life impact scenarios, rotational injuries and how they occur. 

Separate Box - CHECKLIST

Checklist for choosing a safety helmet

There are many factors when choosing a safety helmet. Here are a few to consider:

Rotational management

Ensure the helmet is designed to help address rotational motion, for example, with a low-friction layer like the Mips safety system intended to help reduce rotational motion to the head during certain angled impacts. 

Comfort and fit

You’ll likely be wearing the helmet for long periods, so make sure it’s comfortable will ensure that you enjoy wearing it and will keep it on throughout your work activities.

Safety certifications

Most construction helmets available to consumers must meet certain safety requirements. Still, it is best to double-check that it is up to date with the latest regulations in your particular line of work.

Brand and style

There are plenty of great choices of hard hats available today. Be sure to choose one from a brand you know and trust, with a fit and style you’ll enjoy wearing.

Chris Tidy is product specialist at Mips and founder of Hard Hat Awareness Week. For more information, visit